Damping Off

A zinnia seedling, felled by damping off. Photo: Suzanne DeJohn

When the stems of young plants wither at the soil level and then topple over, they have probably been killed by a disease known as damping off. The culprit is actually pythium, a common fungus. The spores of this fungus require cool, wet soil in order to infect plant tissues. Pythium can also infect seeds as they are germinating, causing seedlings to rot before they make it to the soil surface.

Prevention and Control

Use a well-drained growing medium when starting seeds indoors or in a greenhouse. Allow the growing medium to become relatively dry between waterings.